Satellite navigation device

ABSTRACT

A pseudo range is corrected with high accuracy using a pseudo range correction method that incorporates carrier smoothing. A code pseudo range correction unit ( 19 ) performs carrier smoothing of an L1 code pseudo range (PR L1 (i)) by the temporal change (ΔADR L1 (i)) in an L1 carrier phase, and performs carrier correction of a code ionosphere delay (I PRL1 (i)) by the temporal change (ΔI ADRL1 (i)) in a carrier ionosphere delay. The code pseudo range correction unit ( 19 ) performs ionosphere delay correction by subtracting the corrected ionosphere delay (I′ L1 sm(i)) from the L1 code pseudo range (PR L1 sm(i)) after smoothing processing. At this time, a direction of the delay in the temporal change (ΔI ADRL1 (i)) in the carrier ionosphere delay included in the temporal change (ΔADR L1 (i)) in the L1 carrier phase is matched with a direction of the delay in the temporal change (ΔI ADRL1 (i)) in the carrier ionosphere delay used to calculate the corrected ionosphere delay (I′ L1 sm(i)).

TECHNICAL FIELD

The present invention relates to a satellite navigation device forperforming positioning and generation of a reference signal based on asatellite signal from a navigation satellite.

BACKGROUND OF THE INVENTION

Currently, there are various kinds of satellite navigation devices thatperform positioning and generation of a reference signal such as 1PPS byusing the GNSS (Global Navigation Satellite System). In such satellitenavigation devices, the positioning and the generation of the referencesignal are performed based on navigation signals from a plurality ofnavigation satellites. Here, since the GNSS includes a plurality ofsystems controlled by different administrators, a case of the GPS(Global Positioning System) is described below as an example.

In the GPS, an L1 wave and an L2 wave having frequencies different fromeach other are carrier waves to which a pseudo-noise code and anavigation message are overlaid. Accordingly, each of the GPS satellitesgenerates a GPS signal. Hereinafter, the GPS signal using the L1 wave isreferred to as an L1 signal and the GPS signal using the L2 wave isreferred to as an L2 signal. In each of the GPS satellites, the L1signal in synchronization with the L2 signal goes on the air. Thesatellite navigation device receives the synchronized signal.

The satellite navigation device calculates a pseudo range P for each GPSsatellite based on the pseudo-noise code upon receiving the GPS signaland estimates a position and a receiver time error based on the pseudorange P. In this estimate operation, precision of the pseudo rangeaffects precision of a result of, for example, the positioning. However,since the pseudo range has a margin of error, correction processing forcorrecting the pseudo range becomes essential in order to achieve, forexample, positioning with high precision. Currently, various kinds ofcorrection processing for correcting the pseudo range are proposed, forexample a method of smoothing the pseudo range with a carrier phase anda method of correcting the pseudo range with the ionosphere delay.

For example, in Patent Document 1, after an ionosphere delay amount ofthe L1 signal is calculated based on the pseudo range of the L1 signaland the pseudo range of the L2 signal to smoothen the ionosphere delayamount, the smoothened amount is differentiated from the pseudo range ofthe L1 signal. Accordingly, the ionosphere delay correction isperformed.

In Patent Document 2, an ionosphere-free code pseudo range is calculatedbased on the pseudo range of the L1 signal and the pseudo range of theL2 signal, and an ionosphere-free carrier phase is calculated based on acarrier phase of the L1 signal and a carrier phase of the L2 signal.Then, the ionosphere-free carrier phase is differentiated from theionosphere-free code pseudo range to smoothen the resulting value forthe correction.

In addition to the above, there is another method that performs typicalcarrier smoothing. In this case, the ionosphere delay amount after thecarrier smoothing is differentiated from the pseudo range after thecarrier smoothing, thereby achieving the ionosphere delay correction ofthe pseudo range.

Patent Document 1: JP2008-51567A

Patent Document 2: JP2007-278708A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the method using the above described carrier smoothing,there is a possible problem as described below and thus, despite thatthe calculated pseudo range is corrected, the calculated value comesgradually away from a true pseudo range as illustrated in the belowdescribed FIG. 3.

In the carrier smoothing of the pseudo range according to a typical onefrequency channel, an operation represented by Equation (1) isperformed, in which a current smoothened pseudo range is PRsm(i), acurrent observed pseudo range is PR(i), a previous smoothened pseudorange is PRsm(i−1), a time variation amount of an observed carrier phasefrom the previous to current is ΔADR(i), and a weighting coefficient isk.

$\begin{matrix}{{{PRsm}(i)} = {{\frac{1}{k}{{PR}(i)}} + {\frac{k - 1}{k}\left( {{{PRsm}\left( {i - 1} \right)} + {\Delta\;{{ADR}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

In the carrier smoothing (the carrier correction) of the typical codeionosphere delay, an operation represented by Equation (2) is performed,in which a current smoothing ionosphere delay is Ism(i), the ionospheredelay according to the current observed pseudo range is I_(PR)(i), aprevious smoothened ionosphere delay is Ism(i−1), a variation amount ofthe ionosphere delay amount according to the observed carrier phase fromthe previous to current is ΔI_(ADR)(i), and the weighting coefficient isk similar to the case of the pseudo range.

$\begin{matrix}{{{Ism}(i)} = {{\frac{1}{k}{I_{PR}(i)}} + {\frac{k - 1}{k}\left( {{{Ism}\left( {i - 1} \right)} + {\Delta\;{I_{ADR}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(2)}\end{matrix}$

As described above, after both of the pseudo range and the ionospheredelay relating to a code are smoothened, the ionosphere delay correctionfor the pseudo range is performed by subtracting the smoothened pseudorange PRsm(i) from the smoothened ionosphere delay Ism(i). In otherwords, the above corresponds to an execution of subtracting Equation (2)from Equation (1) to further perform an operation of Equation (3).

$\begin{matrix}{{{{PRsm}(i)} - {{Ism}(i)}} = {{\frac{1}{k}\left( {{{PR}(i)} - {I_{PR}(i)}} \right)} + {\frac{k - 1}{k}\left( {{{PRsm}\left( {i - 1} \right)} - {{Ism}\left( {i - 1} \right)} + {\Delta\;{{ADR}(i)}} - {\Delta\;{I_{ADR}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

Here, since an effect of the ionosphere to the carrier phase works in adirection where a short pseudo range is observed, the time variationamount ΔADR(i) of the carrier phase is represented by Equation (4) basedon the time variation amount Δr(i) of a true range between thenavigation satellite and the receiver (the satellite navigation device)and the time variation amount ΔI_(ADR)(i) of the ionosphere delayamount.ΔADR(i)=Δr(i)−ΔI _(ADR)(i)  Equation (4)

When Equation (4) is substituted by Equation (3), Equation (5) isobtained.

$\begin{matrix}{{{{PRsm}(i)} - {{Ism}(i)}} = {{\frac{1}{k}\left( {{{PR}(i)} - {I_{PR}(i)}} \right)} + {\frac{k - 1}{k}\left( {{{PRsm}\left( {i - 1} \right)} - {{Ism}\left( {i - 1} \right)} + {\Delta\;{r(i)}} - {{2 \cdot \Delta}\;{I_{ADR}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(5)}\end{matrix}$

As shown in Equation (5), PR(i)−I_(PR)(i) and PRsm(i−1)−Ism(i−1) areterms that the ionosphere delay is removed from the pseudo rangeincluding an effect of the ionosphere delay. Further, Δr(i) is the timevariation amount of the true range between the satellite and thereceiver without the ionosphere delay. Accordingly, the right-hand sideof the Equation (5) is composed of the sum of the term of{PR(i)−I_(PR)(i)} and the term of {PRsm(i−1)−Ism(i−1)}, in which theionosphere delay is corrected, and a term of {−2×ΔI_(ADR)(i)}.Therefore, the effect of the ionosphere delay cannot be removed.

Therefore, in the method combined with the typical carrier smoothing,despite of the correction of the ionosphere delay, the right-hand sidedoes not become a term of only the pseudo range but becomes a termalways added with −2ΔI_(ADR)(i), and resulting in being a value shiftedfrom a true pseudo range. Since such a term is added at everycalculation of the pseudo range, the pseudo range which is supposed tohave been corrected further comes away from the true pseudo range.

To resolve the above problem, the present invention is directed to asatellite navigation device that can correct a pseudo range with highprecision even with a method of correcting the pseudo range combinedwith the carrier smoothing.

Means for Solving the Problem

The invention relates to satellite navigation device for calculating acode pseudo range based on a navigation signal from a navigationsatellite. The satellite navigation device includes a pseudo rangecorrection module for correcting the code pseudo range that issmoothened based on a carrier phase, by performing an ionosphere delaycorrection with a code ionosphere delay. The pseudo range correctionmeans matches a direction of a carrier ionosphere delay contained in thecarrier phase with a direction of the code ionosphere delay to correctthe code pseudo range.

Further, the pseudo range correction module of the satellite navigationdevice according to the invention may match the direction of the carrierionosphere delay contained in the carrier phase with the direction ofthe code ionosphere delay by, specifically, matching a shiftingdirection of the carrier phase due to a first carrier ionosphere delaycontained in the carrier phase used in smoothing with a correctiondirection of a second carrier ionosphere delay for a carrier correctionof the code ionosphere delay used in the ionosphere delay.

In this configuration, since the shifting direction of the carrier phasedue to the first carrier ionosphere delay contained in the carrier phasewhen the code pseudo range is smoothened with the carrier phase matchesthe correction direction of the second carrier ionosphere delay for thecarrier correction of the code ionosphere delay, numerical numbers andsymbols in the operation equations of the first carrier ionosphere delayand the second carrier ionosphere delay mathematically match with eachother. Therefore, when the ionosphere delay correction is performed bysubtracting the code ionosphere delay after the carrier correction withthe carrier ionosphere delay from the code pseudo range after smoothenedwith the carrier phase, the first carrier ionosphere delay contained inthe carrier phase for smoothing is balanced out with the second carrierionosphere delay for the carrier correction of the code ionospheredelay. Accordingly, an effect of the ionosphere delay is removed fromthe code pseudo range after the correction thereof by the pseudo rangecorrection module.

Further, the satellite navigation device according to the invention mayinclude a positioning operation module for performing a positioningoperation by using the code pseudo range corrected by the pseudo rangecorrection module.

In this configuration, the code pseudo range corrected with highprecision as described above is used, thereby a positioning result canbe obtained with high precision.

Further, the satellite navigation device according to the invention mayfurther include a reference signal generation module for generating areference clock signal by using a clock offset obtained by thepositioning operation.

In this configuration, the above described positioning operation isperformed with high precision, and therefore, a high-precision clockoffset can be obtained. As a result, a high-precision reference signalcan be generated.

Effect of the Invention

According to the aspects of the present invention, the code pseudo rangewithout the effect of the ionosphere delay can be obtained with highprecision.

BEST MODE FOR CARRYING OUT THE INVENTION

A satellite navigation device of a present embodiment is described belowwith reference to the accompanying drawings. In the followingdescription, the GPS is described as an example; however, the followingconfiguration and processing can be applied also to the other GNSS.

FIG. 1A is a block diagram illustrating main components of a satellitenavigation device 1 of this embodiment. FIG. 1B is a block diagramillustrating main components of a code pseudo range correction module 19illustrated in FIG. 1A.

As illustrated in FIG. 1, the satellite navigation device 1 of thisembodiment includes an L1 receiving module 11, an L2 receiving module12, an L1 pseudo range calculation module 13, an L1 carrier phasecalculation module 14, an L2 pseudo range calculation module 15, an L2carrier phase calculation module 16, a code ionosphere delay calculationmodule 17, a carrier ionosphere delay calculation module 18, a codepseudo range correction module 19, and a positioning operation module20.

The L1 receiving module 11 receives a navigation signal received by anantenna 100 from a navigation satellite to demodulate it, outputs, forexample, a navigation message to the L1 pseudo range calculation module13, and outputs carrier phase information to the L1 carrier phasecalculation module 14. The L2 receiving module 12 receives thenavigation signal received by the antenna 100 from a positioningsatellite to demodulate it, outputs, for example, a navigation messageto the L2 pseudo range calculation module 15, and outputs carrier phaseinformation to the L2 carrier phase calculation module 16.

The L1 pseudo range calculation module 13 calculates an L1 code pseudorange PR_(L1)(i) at a predetermined time cycle based on, for example,the navigation message. The L1 code pseudo range PR_(L1)(i) is outputtedto the code ionosphere delay calculation module 17 and the code pseudorange correction module 19.

The L2 pseudo range calculation module 15 calculates an L2 code pseudorange PR_(L1)(i) concurrently with each piece of information of the L1based on, for example, the navigation message. The L2 code pseudo rangePR_(L2)(i) is outputted to the code ionosphere delay calculation module17.

The L1 carrier phase calculation module 14 calculates an L1 carrierphase ADR_(L1)(i) concurrently with the code pseudo range PR_(L1)(i)based on the carrier phase information of the L1 signal. The L1 carrierphase ADR_(L1)(i) is outputted to the carrier ionosphere delaycalculation module 18 and the code pseudo range correction module 19.

The L2 carrier phase calculation module 16 calculates an L2 carrierphase ADR_(L1)(i) concurrently with the code pseudo range PR_(L1)(i)based on the carrier phase information of the L2 signal. The L2 carrierphase ADR_(L1)(i) is outputted to the carrier ionosphere delaycalculation module 18.

The code ionosphere delay calculation module 17 calculates an L1 codeionosphere delay I_(PRL1)(i) at each timing by using the followingEquation (6).

$\begin{matrix}{{I_{{PRL}\; 1}(i)} = {\frac{f_{L\; 2}^{2}}{f_{L\; 1}^{2} - f_{L\; 2}^{2}}\left( {{{PR}_{L\; 2}(i)} - {{PR}_{L\; 1}(i)}} \right)}} & {{Equation}\mspace{14mu}(6)}\end{matrix}$

The carrier ionosphere delay calculation module 18 calculates a timevariation amount ΔI_(ADRL1)(i) of the carrier ionosphere delay at eachtiming by using the following Equation (7).

$\begin{matrix}{{\Delta\;{I_{{ADRL}\; 1}(i)}} = {\frac{f_{L\; 2}^{2}}{f_{L\; 1}^{2} - f_{L\; 2}^{2}}\left( {{{\lambda_{L\; 1} \cdot \Delta}\;{{ADR}_{L\; 1}(i)}} - {{\lambda_{L\; 2} \cdot \Delta}\;{{ADR}_{L\; 2}(i)}}} \right)}} & {{Equation}\mspace{14mu}(7)}\end{matrix}$

Here, λ_(L1) and λ_(L2) are a wavelength of the L1 signal and awavelength of the L2 signal, respectively. ΔADR_(L1)(i) represents atime variation amount of the L1 carrier phase ADR_(L1)(i) from onetiming before to current and ΔADR_(L2)(i) represents a time variationamount of the L2 carrier phase ADR_(L2)(i) from one timing before tocurrent.

The code ionosphere delay I_(PRL1)(i) calculated in the code ionospheredelay calculation module 17 and the time variation amount ΔI_(ADRL1)(i)of the carrier ionosphere delay calculated in the carrier ionospheredelay calculation module 18 are outputted to the code pseudo rangecorrection module 19.

The code pseudo range correction module 19 includes a code pseudo rangecarrier smoothing module 191, a code ionosphere delay carrier correctionmodule 192, and a code pseudo range ionosphere correction module 193.The code pseudo range correction module 19 corrects the L1 code pseudorange PR_(L1)(i) by using the following principle and outputs theresulting value to the positioning operation module 20.

The code pseudo range carrier smoothing module 191 performs the carriersmoothing for the L1 code pseudo range PR_(L1)(i) by using a weightingaverage obtained by the above Equation (1). In other words, the codepseudo range carrier smoothing module 191 calculates an L1 code pseudorange PR_(L1)sm(i) after the smoothing processing by using the followingEquation (8).

$\begin{matrix}{{{PR}_{L\; 1}{{sm}(i)}} = {{\frac{1}{k}{{PR}_{L\; 1}(i)}} + {\frac{k - 1}{k}\left( {{{PR}_{L\; 1}{{sm}\left( {i - 1} \right)}} + {\Delta\;{{ADR}_{L\; 1}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(8)}\end{matrix}$

Here, the PR_(L1)sm(i) is the L1 code pseudo range after the smoothingprocessing at a current timing, the PR_(L1)sm(i−1) is the L1 code pseudorange after the smoothing processing at one timing before, and k is aconstant for determining a weight and can be changed according to aspecification.

The code ionosphere delay carrier correction module 192 performs acarrier correction for the code ionosphere delay I_(PRL1)(i) by usingthe following Equation (9). In other words, the code ionosphere delaycarrier correction module 192 calculates the code ionosphere delayI′_(L1)sm(i) after the carrier correction by using the Equation (9).

$\begin{matrix}{{I_{L\; 1}^{\prime}{{sm}(i)}} = {{\frac{1}{k}{I_{{PRL}\; 1}(i)}} + {\frac{k - 1}{k}\left( {{I_{L\; 1}^{\prime}{{sm}\left( {i - 1} \right)}} - {\Delta\;{I_{{ADRL}\; 1}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(9)}\end{matrix}$

Here, as represented by the Equation (9), in the present invention, thecarrier correction is performed according to an operation different fromthe carrier smoothing of the typical code ionosphere delay representedby the above described Equation (2). More specifically, when correctingthe code ionosphere delay, the operation is performed, in which the codeionosphere delay I′_(L1)sm(i−1) after the carrier correction of onetiming before is not added with the time variation ΔI_(ADRL1)(i) of thecarrier ionosphere delay (a typical method) but is subtracted by thetime variation ΔI_(ADRL1)(i) of the carrier ionosphere delay.

The processing is performed based on delay directions of the codeionosphere delay and the carrier ionosphere delay being different fromeach other. More specifically, the code ionosphere delay works in adirection where the pseudo range becomes longer while the carrierionosphere delay works in a direction where the pseudo range becomesshorter. In view of the above, a symbol of the time variation amountΔI_(ADRL1)(i) of the carrier ionosphere delay in the equation of thecode ionosphere delay I′_(L1)sm(i) after the carrier correction isinverted such that the directions match with each other.

The code pseudo range ionosphere delay correction module 193 subtractsthe code ionosphere delay I′_(L1)sm(i) after the carrier correction,which is calculated in the Equation (9), from the L1 code pseudo rangePR_(L1)sm(i) after the smoothing processing, which is calculated in theEquation (8).

$\begin{matrix}{{{{PR}_{L\; 1}{{sm}(i)}} - {I_{L\; 1}^{\prime}{{sm}(i)}}} = {{\frac{1}{k}\left( {{{PR}_{L\; 1}(i)} - {I_{{PRL}\; 1}(i)}} \right)} + {\frac{k - 1}{k}\left( {{{PR}_{L\; 1}{{sm}\left( {i - 1} \right)}} - {I_{L\; 1}^{\prime}{{sm}\left( {i - 1} \right)}} + {\Delta\;{{ADR}_{L\; 1}(i)}} + {\Delta\;{I_{{ADRL}\; 1}(i)}}} \right)}}} & {{Equation}\mspace{14mu}(10)}\end{matrix}$

This equation corresponds to performing the ionosphere delay correctionfor the L1 code pseudo range PR_(L1)sm(i) after the smoothing processingby using the ionosphere delay after the carrier correction.

Here, an effect of the ionosphere delay with respect to the carrierphase works in the direction where the pseudo range is observed short,therefore the time variation amount ΔADR_(L1)(i) of the L1 carrier phaseis represented by the following equation:ΔADR _(L1)(i)=Δr(i)−ΔI _(ADRL1)(i)  Equation (11)

by using a time variation amount Δr(i) of a true range between thesatellite and the receiver and the time variation amount ΔI_(ADRL1)(i)of the ionosphere delay.

Therefore, by substituting the Equation (11) into Equation (10), thefollowing (Equation (12)), meaning the L1 code pseudo range is subjectedto the ionosphere delay correction with the code ionosphere delay, canbe obtained.

$\begin{matrix}{{{{PR}_{L\; 1}{{sm}(i)}} - {I_{L\; 1}^{\prime}{{sm}(i)}}} = {{\frac{1}{k}\left( {{{PR}_{L\; 1}(i)} - {I_{{PRL}\; 1}(i)}} \right)} + {\frac{k - 1}{k}\left( {{{PR}_{L\; 1}{{sm}\left( {i - 1} \right)}} - {I_{L\; 1}^{\prime}{{sm}\left( {i - 1} \right)}} + {\Delta\;{r(i)}}} \right)}}} & {{Equation}\mspace{14mu}(12)}\end{matrix}$

In other words, the time variation amount ΔI_(ADRL1)(i) of the carrierionosphere delay contained in the time variation amount ΔADR_(L1)(i) ofthe L1 carrier phase corresponding to a first carrier ionosphere delayof the invention is balanced out with the time variation amountΔI_(ADRL1)(i) of the carrier ionosphere delay contained in the equationof the carrier correction of the code ionosphere delay I_(PRL1)(i)corresponding to a second carrier ionosphere delay of the invention.

Here, the term of (1/k)×(PR_(L1)(i)−I_(PRL1)(i)) in the right-hand sideof Equation (12) corresponds to performing the ionosphere delaycorrection for the current L1 code pseudo range PR_(L1)(i) by using thecurrent code ionosphere delay I_(PRL1)(1). Similarly, the term of((k−1)/k)×(PR_(L1)sm(i−1)−I′_(L1)sm(i−1)) corresponds to correcting theL1 code pseudo range PR_(L1)sm(i−1) after the smoothing processing ofone timing before by using the ionosphere delay I′_(L1)sm(i−1) after thecarrier correction of one timing before.

As described above, by performing the operation as represented by theEquation (12), even if the ionosphere delay correction is performed withthe carrier-corrected ionosphere delay after the L1 code pseudo range issubjected to the carrier smoothing, an effect of the time variationamount ΔI_(ADRL1)(i) of the carrier ionosphere delay does not remain asrepresented by the conventional Equation (5) and thus an effect of thetime variation amount ΔI_(ADRL1)(i) of the carrier ionosphere delay withrespect to the corrected L1 code pseudo range can be removed.

In the above description, such an example is described that the codepseudo range correction module 19 includes the code pseudo range carriersmoothing module 191, the code ionosphere delay carrier correctionmodule 192, and the code pseudo range ionosphere delay correction module193, and that the L1 pseudo range calculation module 13, the L1 carrierphase calculation module 14, the L2 pseudo range calculation module 15,the L2 carrier phase calculation module 16, the code ionosphere delaycalculation module 17, and the carrier ionosphere delay calculationmodule 18 are independent functional modules. However, these modules mayserve as a single code pseudo range generation module to correct thecode pseudo range according to the flow described as follows.

FIG. 2 is a flowchart illustrating a flow of correction processing ofthe code pseudo range of the satellite navigation device 1 of thisembodiment.

Firstly, the code pseudo range generation module calculates the L1 codepseudo range PR_(L1)(i) and the L2 code pseudo range PR_(L2)(i) at everypredetermined timing based on, for example, the navigation message(S101).

The code pseudo range generation module calculates the L1 carrier phaseADR_(L1)(i) based on the carrier phase information of the L1 signal, andcalculates the L2 carrier phase ADR_(L2)(i) based on the carrier phaseinformation of the L2 signal (S102).

The code pseudo range generation module calculates the L1 codeionosphere delay I_(PRL1)(i) at each timing by using the above describedEquation (6) (S103). The code pseudo range generation module calculatesthe time variation amount ΔI_(ADRL1)(i) of the carrier ionosphere delayat each timing by using the above described Equation (7) (S104).

The code pseudo range generation module performs the ionosphere delaycorrection of the carrier-smoothed L1 code pseudo range PR_(L1) by usingthe time variation amount ΔADR_(L1) of the carrier phase, the codeionosphere delay I_(PRL1), and the time variation amount ΔI_(ADRL1) ofthe carrier ionosphere delay, based on the above described equations(8), (9) and (10) (S105).

The effect of the time variation amount ΔI_(ADRL1)(i) of the carrierionosphere delay can be removed even with the above processing that theL1 code pseudo range after the carrier smoothing is subjected to theionosphere delay correction with the code ionosphere delay after thecarrier correction.

FIG. 3 is a graph illustrating values of the L1 code pseudo range in therespective cases where the method of this embodiment is used, where theconventional method is used, and where the carrier smoothing is notperformed. In FIG. 3, a horizontal axis represents a time passage and avertical axis represents a pseudo range error from the true pseudorange.

As it is illustrated in FIG. 3, by using the method of this embodiment,the code pseudo range corrected with the ionosphere delay after thecarrier smoothing and carrier correction approximately matches the truecode pseudo range without the values being varied along the passage oftime.

As described above, by using the configuration and the method of thisembodiment, the code pseudo range can be calculated with high precision.

Thus calculated code pseudo range is applied to the positioningoperation module 20. The positioning operation module 20 performs apositioning of its own device (receiver) by using the code pseudo rangeaccording to a known method. Accordingly, the positioning can beperformed with high precision. Further, the positioning operation module20 includes a reference signal generation circuit, and thereby areference signal such as 1PPS can also be outputted. At the time, sincethe code pseudo range can be obtained with high precision, the clockoffset of the own device (receiver) can be obtained with high precision.As a result, the reference signal can be generated with high precision.

In the configuration and the processing of this embodiment, since thecode pseudo range including the ionosphere delay can be corrected withhigh precision, it is not necessary to use a ionosphere-freecombination. Accordingly, an effective correction of the code pseudorange is achieved with respect to the satellite navigation deviceconcurrently using a differential positioning system. In other words, ina range where differential information can be used, the ionosphere delaycorrection can be performed with the ionosphere delay informationobtained by the differential information after the carrier smoothing ofthe code pseudo range. Therefore, even in a range where the differentialinformation cannot be used, the correction of the code pseudo range canbe performed with high precision by using the above described method.

In the above description, a case where the L1 code pseudo range iscorrected is exemplified, the L2 code pseudo range can also be correctedin a similar manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 includes a block diagram illustrating main components of asatellite navigation device 1 and a block diagram illustrating maincomponents of a code pseudo range correction module 19 according to anembodiment.

FIG. 2 is a flowchart illustrating a flow of correction processing of acode pseudo range of the satellite navigation device 1 according to theembodiment of the present invention.

FIG. 3 is a graph illustrating values of an L1 code pseudo range ofrespective cases where a method of the embodiment of the presentinvention is used, where a conventional method is used, and where acarrier smoothing is not performed.

DESCRIPTION OF THE NUMERICAL NUMBERS

1: satellite navigation device; 11: L1 receiving module; 12: L2receiving module; 13: L1 pseudo range calculation module; 14: L1 carrierphase calculation module; 15: L2 pseudo range calculation module; 16: L2carrier phase calculation module; 17: code ionosphere delay calculationmodule; 13: carrier ionosphere delay calculation module; 19: code pseudorange correction module; 191: code pseudo range carrier smoothingmodule; 192: code ionosphere delay carrier correction module; 193: codepseudo range ionosphere delay correction module; 20: positioningoperation module; 100: antenna

What is claimed is:
 1. A satellite navigation device for calculating acode pseudo range based on a navigation signal from a navigationsatellite, comprising: a pseudo range correction module for correctingthe code pseudo range that is smoothened based on a carrier phase, byperforming an ionosphere delay correction with a code ionosphere delay,wherein the pseudo range correction module matches a direction of acarrier ionosphere delay contained in the carrier phase with a directionof the code ionosphere delay to correct the code pseudo range; andwherein the pseudo range correction module matches the direction of thecarrier ionosphere delay contained in the carrier phase with thedirection of the code ionosphere delay by matching a shifting directionof the carrier phase due to a first carrier ionosphere delay containedin the carrier phase used in the smoothing of the code pseudo range witha correction direction of a second carrier ionosphere delay for acarrier correction of the code ionosphere delay used in the ionospheredelay.
 2. The satellite navigation device of claim 1, further comprisinga positioning operation module for performing a positioning operation byusing the code pseudo range corrected by the pseudo range correctionmodule.
 3. The satellite navigation device of claim 2, furthercomprising a reference signal generation module for generating areference clock signal by using a clock offset obtained by thepositioning operation.